Fire extinguishers are known in the art for detecting the increase in temperature of an enclosure due to fire occurrence and operating to extinguish the fire at the earlier stage. These known devices may be roughly classified into a device in which the opening of a vessel filled with a fire extinguishing gas under an elevated pressure is covered with a sealing cap which may be ruptured upon detection of a fire to permit the gas within the vessel to be injected into the enclosure; and a device comprising a vessel containing a high pressure gas and a tank containing a fire extinguishing solution and in which a sealing cap for the opening of the vessel is broken upon a fire detection to permit the gas within said vessel to flow into said tank for driving the solution into the enclosure.
An actuating device used in these fire extinguishers for breaking the sealing cover upon a fire occurrence is so designed that a striker acted on by a spring urged towards a sealing cover or a hammer acted on by a spring for applying an impact on a striker head of the sealing cover is held in a stationary position by a holding member made of heat fusible material such as solder. The holder may be fused under the heat of the fire to permit the striker to impinge and sever the sealing cover. With such known devices, the holder made of heat fusible material is placed perpetually under a shearing or tensile force and therefore may be deteriorated with time due to creep and temperature changes in the enclosure, thus causing the operation of the fire extinguisher on an occasion other than an actual fire.
So far, a cylindrical or spherical tank was used for containing a fire extinguishing solution. Such a tank has a poor appearance when mounted to the ceiling because of increased vertical size and may be undesirable to residents. Moreover, with such tank shapes, a gas vessel and means for breaking a seal on the gas vessel must be provided within the tank, thus complicating the structure of the device.